Geogarage

Saturday, March 28, 2015

I met my husband in the middle of the sea link


For the Moken people of Southeast Asia, the sea provides nearly everything a person might need.
It offers food to eat, a comfortable place to live (assuming one owns the appropriate vessel), and, sometimes, love.
Members of this ocean-faring ethnic group – often called “Sea Gypsies” – roam the Andaman Sea off the coasts of Thailand and Myanmar.
The Moken travel on small, handcrafted wooden boats called kabangs, from which they skillfully procure fresh meals of fish, scallops, and clams, using nothing more complicated than a simple spear and a remarkable ability to hold their breath.
To see the full story: junglesinparis.com/stories/49

This film was edited exclusively for Jungles in Paris using footage from the feature "Sailing a Sinking Sea"(2015), which premieres at SXSW March 2015..
Feature film website: cargocollective.com/sailingasinkingsea

Links :
 

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Friday, March 27, 2015

Antarctic ice shelves are melting dramatically, study finds link


A new study published by Science and led by Scripps Institution of Oceanography at UC San Diego researchers has revealed that the thickness of Antarctica’s floating ice shelves has recently decreased by as much as 18 percent in certain areas over nearly two decades, providing new insights on how the Antarctic ice sheet is responding to climate change.
Data from nearly two decades of satellite missions have shown that the ice volume decline is accelerating.

From The Guardian by


The ice around the edge of Antarctica is melting faster than previously thought, potentially unlocking metres of sea-level rise in the long-term, researchers have warned.
A team of US scientists looked at 18 years’ worth of satellite data and found the floating ice shelves that skirt the continent are losing 310km3 of ice every year.
One shelf lost 18% of its thickness during the period.
The loss of ice shelves does not contribute much directly to sea level rise.
But they act like a cork in a bottle at the point where glaciers meet the sea – jamming the flow of ice from the massive ice sheets of east and west Antarctica.

 Satellite view of a large iceberg separating from Antarctica’s Pine Island Glacier, where ice loss has doubled in speed over the last 20 years.
Photograph: MODIS/Aqua/NASA




Professor Andrew Shepherd, director of the Centre for Polar Observation and Modelling at the University of Leeds, said the rates of ice loss were unsustainable and could cause a major collapse.
This is already occurring at the massive Pine Island glacier, where ice loss has doubled in speed over the last 20 years as its blocking ice shelf has melted.
“This is a real concern, because such high rates of thinning cannot be sustained for much longer, and because in the places where Antarctic ice shelves have already collapsed this has triggered rapid increases in the rate of ice loss from glaciers above ground, causing global sea levels to rise,” he said. 

 Changes to the thickness and volume of Antarctica's ice shelves between 1994 and 2012.
Credit: Paolo, et al./Science
The new research, published in the journal Science on Thursday, discovered for the first time that ice shelf melt is accelerating.
Dr Paul Holland, a climate scientist at the British Antarctic Survey (BAS), said the loss of the shelves would speed the complete collapse of the west Antarctic ice sheet, which would eventually cause up to 3.5m of sea level rise.
But he said it was highly unlikely this would occur this century.
He said the “worst case scenario” for 2100 was that ice sheets would contribute an additional 70cm to the sea level rise caused by the warming of the ocean.

 Antarctica's Brunt Ice Shelf.
Credit: Michael Studinger/NASA.

The UN’s climate science body has not previously included the ice sheets of Antarctica and Greenland in its predictions for future sea level rise because scientists are not certain how fast they will slide into the ocean.

 Pine Island Glacier on Sentinel-1A’s radar
This image combining two scans by Sentinel-1A’s radar shows that parts of the Pine Island glacier flowed about 100 m (in pink) between 3 March and 15 March 2015.
Light blue represents stable ice on either side of the stream.
Pine Island is the largest glacier in the West Antarctic Ice Sheet and one of the fastest ice streams on the continent, with an average of over 4 km per year.
About a tenth of the ice sheet drains out to the sea by way of this glacier.
With its all-weather, day and night radar vision, the Sentinel-1 mission is an important tool for monitoring polar regions and the effects that climate change has on ice.

Holland said: “What humanity needs to know is what’s the sea level rise in 2100 and the biggest source of uncertainty in that is what’s going to happen to the ice sheets.”
Over the past decade the loss of ice shelf volume in Antarctica increased from 25km3 to 310km3 every year.
It is unclear whether the loss of ice is directly related to man-made climate change or a cyclical change in ocean currents.
But the extra sea level rise from ice sheets will exacerbate the rise caused by the expansion of oceans as the world warms.
Professor David Vaughan, director of science at BAS, said the findings would help scientists to make more accurate predictions about future sea level rise.
“The rate of ice loss, especially when considered in terms of the percentage of ice lost in the last two decades, is dramatic. This research is a significant step towards improving our ability to predict the future of the Antarctic ice sheet and its contribution to global sea level rise.”

 Schematic diagram of an Antarctic ice shelf showing the processes causing the volume changes measured by satellites.
Ice is added to the ice shelf by glaciers flowing off the continent and by snowfall that compresses to form ice.
Ice is lost when icebergs break off the ice front, and by melting in some regions as warm water flows into the ocean cavity under the ice shelf.
Under some ice shelves, cold and fresh meltwater rises to a point where it refreezes onto the ice shelf.
Helen Amanda Fricker, Professor, Scripps Institution of Oceanography, UC San Diego, Author provided

The western coast ice shelves contributed the majority of the ice loss.
The rate of loss increased by 70% in the last decade.
Two shelves in this region could completely disappear within a century.
Conversely, there were some areas in east Antarctica where the shelves stayed stable or grew slightly. Vaughan said the regional variations were predicted by previous studies.
Holland said it was important not to confuse floating ice shelves, which can be up to 2km thick, with the much thinner sea ice.
The one metre thick layer of sea ice around Antarctica has been expanding in recent decades, which some scientists think is because of increasing polar winds, which push the ice further out.

Links :
  • Climate Central : Antarctica’s Icy ‘Doorstops’ Thin; Rising Seas At Risk
  • Scientific America : Antarctica's Ice Shelves Thin, Threaten Significant Sea Level Rise
  • Washington Post : Antarctica’s floating ice shelves, the doorstop of the continent, are melting away
  • NPR : Big Shelves Of Antarctic Ice Melting Faster Than Scientists Thought
  • The Conversation : Shrinking of Antarctic ice shelves is accelerating

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Thursday, March 26, 2015

France SHOM update with the Marine GeoGarage link

new update (17/03/2015) in the France (SHOM) layer

2 charts has been substituted since the last update (October 2014) :

7705   Abords de Mohammadia (replacing chart 6142 Abords de Mohammadia)
7800   Golfe d'Aden et approches (replacing chart 6947 Abords et Partie Est du golfe d'Aden)

All the other charts have been updated according to the new editions :

voir GAN Groupe d'Avis aux Navigateurs en ligne

Today 750 charts including sub-charts from SHOM material are displayed in the Marine GeoGarage.

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The iceberg watch link

Navigators in stressful icy areas

From VovoOceanRace by Agathe Armand

Icebergs.

Drifting blocks of ice detached from the Antarctic glaciers, frozen cubes of a couple of metres – or even tens of kilometres.
They are a polar symbol, an environmental marker – and a huge hazard for the Volvo Ocean Race teams, sailing across the Southern Ocean from Auckland to Itajaí.

 Abu Dhabi Race Team talk us through the iceberg updates they receive on the boat
and Phil Harmer's less technical approach to iceberg detection.

“So far, we’ve detected about 20 of them for the race,” says Franck Mercier of CLS.
The French company has been contracted by the organisers to deliver ice analysis and data that Alicante Race Control then uses to place the ice limits* for Leg 5.

So how exactly do you find an iceberg?
Well, it’s a tiny bit technical, and CLS has to use a lot of different data and up to four satellites for that.
First, the sea temperature.
The colder the water, the more likely they are to find drifting ice.
Currents have an effect, too, pushing it all around the Southern Ocean.
Secondly, the historical data CLS has gathered these past few years – they’ve been assisting several sailing races including the Vendée Globe and the Barcelona World Race.
And finally, the radar techniques.
Now we’re talking.

The brown and red squares are potential icy areas; the green and blue stars are detected icebergs.

CLS is working with space agencies, using their satellites to scan the sea surface in search of ice. They use altimetry techniques to draft a first exclusion zone, and SAR imagery to target the areas identified as potentially dangerous and scan them thoroughly.
Altimetry only spots the biggest icebergs, that is, ones bigger than 300m.
SAR imagery is much more precise, every standard image covering a 500km x 500km area.
SAR satellite sensors can detect smaller bits of ice – up to 50m in the case of a high-resolution picture. That’s as accurate as it gets, and it’s pretty expensive.
“Remember it’s not an exact science,” adds Franck, a French researcher who knows the icebergs by name.
“We’re contributing to decrease the risks, but we don’t suppress it.
“The idea is to detect the biggest icebergs to anticipate the position of the smaller ones, which are still very dangerous for the boats, all of this part of the ocean dynamic.”
Their biggest catch this time around?
A 1km long iceberg, first spotted because of a cold water plume, then “photographed” three times.
Franck and his colleagues have done the calculations – it’s 150m wide, 300m high, underwater part included, and it weighs 25 millions tons, the equivalent of 50 super tankers.
And the current was pushing it north at 1.1 knot, straight towards the fleet’s predicted position.
So they’ve warned Race Management, who moved the ice limits north.
They can change one of the points of this virtual line no later than 30 degrees of longitude before the first boat reaches it.

“There’s definitely plenty of ice around,” comments Simon Fisher. 
Picture : Guo Chuan / Green Dragon Racing
 
Abu Dhabi Ocean Racing’s navigator is sat at the chart table and looks at a satellite picture of the area, wearing a nervous grin.
His boat is currently 2,000 nautical miles away from land – they simply cannot afford to run into drifting ice.
In 2001-02, News Corp sailed through ice and it's not something the sailors recall fondly.
“All the blue dots are icebergs that have been picked up by the various radars," adds Simon.
"So far they’re doing a good job at keeping us out of it.”


It’s a matter of safety – but it goes way beyond that.
“There is very little scientific literature about Antarctic drifting icebergs.
The existing data only goes back 10 years or so, when sailing races took an interest.
“Because there is no record yet, we cannot really link the ice activity in the area to the global warming theme.
We see more of these icebergs, that’s true, but that’s also due to our improved techniques.
“The icebergs of the northern hemisphere come from the Artic polar icecap and are studied more. They’re directly linked to the climate change - and the quantity of sea ice decreases indeed.
“But in Antarctica, there is little change. In fact, the southern ice field tends to increase in winter… it could be one of the consequences of the global warming that causes an increase in the precipitations. These are only hypotheses.”

(picture courtesy of volodiaja)

* Ice limits:A virtual line the fleet must leave to starboard, it can be modified by Race Management depending on the movement of the ice in the southern part of the globe. An imaginary point has been placed every five degrees, drawing a precise contour that can be adapted.
Ice limit changes on March 25:Leg 5 Sailing Instructions Amendment 8 has been posted and communicated to the boats – waypoints 11 and 12 have been moved further north after the detection of a new iceberg close to the ice limit line had been confirmed, between 95 W and 100 W.

Links :

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Wednesday, March 25, 2015

Where is Point Nemo? link

Point Nemo is the location in the ocean that is farthest from land.
You can't get farther away from land than 'Point Nemo.' 

From NOAA

Want to get away from it all?
You can't do better than a point in the Pacific Ocean popularly known as 'Point Nemo,' named after the famous submarine sailor from Jules Verne's Captain Nemo (Twenty Thousand Leagues Under the Sea).

 Map of distance to the nearest coastline (including oceanic islands, but not lakes) with red spots marking the poles of inaccessibility of main landmasses, Great Britain, and the Iberian Peninsula. Thin isolines are 250 km (160 mi) apart; thick lines 1,000 km (620 mi).

 Nemo point with the Marine GeoGarage
(-48.958812, -123.434678)

The oceanic pole of inaccessibility (48°52.6′S 123°23.6′W) is the place in the ocean that is farthest from land.


It lies in the South Pacific Ocean, 2,688 km (1,670 mi) from the nearest lands: Ducie Island (part of the Pitcairn Islands) in the north, Motu Nui (part of the Easter Islands) in the northeast, and Maher Island (near the larger Siple Island, off the coast of Marie Byrd Land, Antarctica) in the south. Chatham Island lies farther west, and Southern Chile in the east.
- see Wikipedia Pole of inaccessibility -

 zoom on Nemo Point watermarked on Google Earth
On Google Earth, a circle with the text "NEMO" printed next to it,
slightly darkened on the actual map itself, can be seen at this point.

By the way, in the The Mysterious Island (L'Île mystérieuse in French) another novel by Jules Verne, there is a reference to a "Lincoln Island", unknown (and fictitious) island also located in the Pacific no and so far (about 1500 Nm) NW from the Nemo Point at 34°57′S 150°30′W


 Map of the fictional Lincoln Island (The Mysterious Island).
This image originally drawn by Jules-Descartes Férat (1819–1889?) was originally featured
in the Hetzel edition of Mysterious Island, and has also been featured in more recent editions 
(this particular instance was scanned from a recent edition).

Links :

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Image of the week : Swirls of color in the Yellow Sea link

NASA, acquired February 24, 2015

From NASA

Water covers 71 percent of Earth’s surface, giving rise to the nickname “the Blue Marble” or “the Blue Planet.”
Satellites that observe ocean color, however, show that it’s not that simple.
Materials in the water—living or otherwise—are often stirred and mixed until the surface swirls with hints of blue, green, tan, white, and brown.

One area where this is extremely apparent is the Yellow Sea, pictured here in an image acquired on February 24, 2015, by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.
“The region of Bohai Sea, Yellow Sea, and East China is one of the most turbid and dynamic ocean areas in the world,” said ocean color expert Menghua Wang of the National Oceanic and Atmospheric Administration.

In the image, the brown area along China’s Subei Shoal is turbid water commonly seen in coastal regions.
According to Wang, shallow water depths, tidal currents, and strong winter winds likely contributed to the mixing of sediment through the water.

 Yellow Sea with the Marine GeoGarage (NGA chart)

Some of the swirls in the image might be due to the Yellow Sea Warm Current, which intrudes into the Yellow Sea in wintertime.
This branch of the Kuroshio Current changes the temperature of the sea surface and brings instability that could be the cause of the relatively dark swirls in the lower-middle part of the image.

Interpreting satellite images of ocean color can be a challenge, especially in complex regions like the Yellow Sea.
Upcoming missions such as the Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) should help scientists to better distinguish the particles and materials in the atmosphere and ocean.

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Tuesday, March 24, 2015

US NOAA update with the Marine GeoGarage link

As our public viewer is not yet available
(currently under construction, upgrading to a new viewer
as Google Maps API v2 is officially no more supported),
this info is primarily intended to our universal mobile application users
(Marine US iPhone-iPad on the Apple Store &
Weather 4D Android -App-in- on the PlayStore)
and also to our B2B customers which use our nautical charts layers
in their own webmapping applications through our GeoGarage API

 NOAA raster chart coverage

16 charts have been updated in the Marine GeoGarage
(NOAA update March 2015, released March 18, 2015)

  • 12243 ed15 York River Yorktown to West Point
  • 12244 ed15 Pamunkey And Mattaponi Rivers
  • 16206 ed9 Nome Hbr. and approaches. Norton Sound;Nome Harbor
  • 16430 ed7 Attu Island Theodore Pt. to Cape Wrangell
  • 16474 ed9 Bay of Islands;Aranne Channel;Hell Gate
  • 16476 ed11 Sweeper Cove. Finger and Scabbard Bays
  • 16484 ed8 Atka Island to Chugul Island Atka Island
  • 16487 ed7 Korovin Bay to Wall Bay-Atka Island;Martin Harbor
  • 16516 ed8 Chernofski Harbor
  • 16521 ed7 Unalaska Island Protection Bay to Eagle Bay
  • 16603 ed9 Kukak Bay. Alaska Peninsula
  • 16706 ed11 Passage Canal incl. Port of Whittier;Port of Whittier
  • 16711 ed3 Port Wells. including College Fiord and Harriman Fiord
  • 17323 ed13 Salisbury Sound. Peril Strait and Hoonah Sound
  • 17330 ed10 West Coast of Baranof Island Cape Ommaney to Byron Bay
  • 17381 ed11 Reb Bay. Prince of Wales Island
  • 17384 ed10 Wrangell Harbor and approaches;Wrangell Harbor
  • 17422 ed10 Behm Canal-western part;Yes Bay
  • 11489 ed40 Intracoastal Waterway St. Simons Sound to Tolmato River
  • 11490 ed21 Approaches to St. Johns River;St. Johns River Entrance
  • 11491 ed39 St. Johns River-Atlantic Ocean to Jacksonville
Today 1026 NOAA raster charts (2236 including sub-charts) are included in the Marine GeoGarage viewer (see PDFs files)


How do you know if you need a new nautical chart?
See the changes in new chart editions.
NOAA chart dates of recent Print on Demand editions

Note : NOAA updates their nautical charts with corrections published in:
  • U.S. Coast Guard Local Notices to Mariners (LNMs),
  • National Geospatial-Intelligence Agency Notices to Mariners (NMs), and
  • Canadian Coast Guard Notices to Mariners (CNMs)
While information provided by this Web site is intended to provide updated nautical charts, it must not be used as a substitute for the United States Coast Guard, National Geospatial-Intelligence Agency, or Canadian Coast Guard Notice to Mariner publications

Please visit the
NOAA's chart update service for more info or the online chart catalog

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